[MHGinTN]

“the “leaven of the Pharisees” Great point!!! He was using metaphor then and in the Upper Room. They would have caught the metaphor immediately in the Upper Room because not too many days before He had taken the time to explain the metaphor of the Pharisee’s leaven, and these Jewish men knew that for all their generations they were to never drink the blood.

[MHGinTN]

Perhaps terycarl does not know that the bread served at Passover and for seven days in unleavened bread, to commemorate/Remember the hasty departure from Egypt, so quickly that they didn't even have time to let the yeast rise in the dough!